UVM Theses and Dissertations
Format:
Print
Author:
Vize, Andrew Robert
Dept./Program:
Electrical Engineering
Year:
2012
Degree:
MS
Abstract:
Submicron particles in automobile exhaust have been of interest to the scientific community for a number of years due to the negative health effects in humans. To date, spectral data relating to the concentration of submicron aerosol particles has been collected in large part with laboratory based instrumentation. Studies using laboratory based instrumentation for on-board monitoring of automobile engine exhaust have been performed but the size, power requirements, and capital investment associated with each instrument makes routine sampling of multiple, largely unaltered, vehicles a daunting task. As such, the work presented herein, considers the development of a lowcost, low-power, self contained, particle sizing instrument with a reduced footprint that can make in-situ studies involving a large number of vehicles a reality.
The Portable Ultrafine Particle Sizer (PUPS) was designed for the purpose of analyzing particles in the ultrafine range (<100 nm). The PUPS is intended to be affixed directly to the chassis of a vehicle with minimal vehicle customization and with no load on the vehicle's electrical system. This ruggedized instrument was designed to withstand the real-wor1d harsh environmental conditions and vibration induced by in-situ on-board sampling. The sampling methodology was inspired by that of the existing laboratory based instrumentation, in that it uses a corona ionizer to induce a charge on aerosol particles which are then interrogated in a reverse differential mobility analyzer (r-DMA).
This thesis details the design, fabrication, and characterization of the corona ionizer suitable for the PUPS apparatus. Design considerations were centered about the geometric, electrical power, and economic constraints ofthe application. Fabrication of the corona ionizer was completed first hand from raw materials. The corona ionizer high voltage needle was fabricated from an off-the-shelf tungsten electrical probe, designed for use in the probing of semiconductor wafers. An extensive characterization of the corona ionizer was carried out with the use of an electrostatic precipitator, custom Faraday cup, TSI 3080 electrostatic classifier, and TSI 3025A ultrafine condensation particle counter. The figures of merit for this study were the intrinsic and extrinsic efficiency of the corona ionizer as well as electrostatic and diffusion loss.
The PUPS corona ionizer has been shown to have high intrinsic charge efficiency, with nearly 100% of particles receiving at least one charge. The extrinsic charge efficiency is lower than expected and was the result of a larger than expected electrostatic loss. The majority of the electrostatic loss is thought to be caused by space charge between unipolar charged particles in high concentration. The diffusion loss was also higher than expected. The corona ionizer meets the size requirements of the PUPS and can be fabricated and maintained very inexpensively due to the use of off the-shelf components.
The Portable Ultrafine Particle Sizer (PUPS) was designed for the purpose of analyzing particles in the ultrafine range (<100 nm). The PUPS is intended to be affixed directly to the chassis of a vehicle with minimal vehicle customization and with no load on the vehicle's electrical system. This ruggedized instrument was designed to withstand the real-wor1d harsh environmental conditions and vibration induced by in-situ on-board sampling. The sampling methodology was inspired by that of the existing laboratory based instrumentation, in that it uses a corona ionizer to induce a charge on aerosol particles which are then interrogated in a reverse differential mobility analyzer (r-DMA).
This thesis details the design, fabrication, and characterization of the corona ionizer suitable for the PUPS apparatus. Design considerations were centered about the geometric, electrical power, and economic constraints ofthe application. Fabrication of the corona ionizer was completed first hand from raw materials. The corona ionizer high voltage needle was fabricated from an off-the-shelf tungsten electrical probe, designed for use in the probing of semiconductor wafers. An extensive characterization of the corona ionizer was carried out with the use of an electrostatic precipitator, custom Faraday cup, TSI 3080 electrostatic classifier, and TSI 3025A ultrafine condensation particle counter. The figures of merit for this study were the intrinsic and extrinsic efficiency of the corona ionizer as well as electrostatic and diffusion loss.
The PUPS corona ionizer has been shown to have high intrinsic charge efficiency, with nearly 100% of particles receiving at least one charge. The extrinsic charge efficiency is lower than expected and was the result of a larger than expected electrostatic loss. The majority of the electrostatic loss is thought to be caused by space charge between unipolar charged particles in high concentration. The diffusion loss was also higher than expected. The corona ionizer meets the size requirements of the PUPS and can be fabricated and maintained very inexpensively due to the use of off the-shelf components.